This invention relates to a charging apparatus, and more particularly to a charging apparatus for use with an electronic device.
Different charging apparatuses for charging an electronic device such as, but not limited to, an analog electronic timepiece, are presently available. Generally, light or electromanetic energy from or a direct connection to an external power source is used to recharge a battery within the timepiece.
A typical charging apparatus employing light energy includes a solar battery as part of a dial plate of the timepiece. The solar battery generates electric power for charging a secondary battery located within the timepiece.
A charging apparatus employing a direct connection to an external power source is disclosed within Japanese Patent Laid-Open Application Nos. 154665/77 and 11846/74 and Japanese Utility Model Publication No. 4240/81. The battery located within the timepiece is charged by connecting a lead between the external power source and a terminal located on the external surface of the timepiece.
A charging apparatus for transferring electromagnetic energy from an external source to the timepiece is disclosed in Japanese Patent Laid-Open Application No. 29783/86. The source of electromagnetic energy is coupled to a charging coil disposed within the timepiece which induces a current for charging a battery also disposed within the timepiece. A counting coincidence circuit of the timepiece counts and thereby controls the length of time during which the battery is charged. The timepiece also includes a motor and a motor driving circuit for regulating the motor. The motor driving circuit maintains the motor in a deenergized (i.e. OFF) state during the charging period. The timepiece also includes compensating circuitry for correcting the time displayed by the timepiece for the charging period when the motor is deenergized. Each of these conventional charging apparatuses has one or more drawbacks. These drawbacks are particularly undesirable when the timepiece is an analog electronic wristwatch.
Charging apparatuses employing a solar battery or a direct connection from an external power source limit the variety of ornamental wristwatch designs which can be used. The limitation is due to the physically small size of the wristwatch. The difficulty in providing a variety of ornamental wristwatch designs is particularly troublesome when the ornamental appearance is commercially significant.
Charging apparatuses which transfer electromagnetic energy to a wristwatch as disclosed in Japanese Patent Laid-Open Application No. 29783/86 adversely affect the movement of a step motor of the wristwatch resulting in improper hand movement of the watch. Motor control circuitry, counting circuitry and circuitry (i.e. consistent means) are required in the timepiece in order to provide continuous and accurate hand movement during the charging period. Such circuitry limits the variety of different ornamental wristwatch designs available and increases the cost of manufacturing an analog electronic wristwatch. This type of charging device also can be used as a window display during charging of the wristwatch. Unfortunately, an undesirable image of the watch is created due to hand movement being halted during the charging period. The magnetic field also adversely affects any other analog timepiece positioned near the window display of the charging device.
It is therefore desirable to provide a charging device for an electronic timepiece such as a wristwatch which is relatively small in size, inexpensive to manufacture and which charges the battery of the wristwatch in a relatively short period of time. The charging device should also consume relatively little energy and increase the efficiency in transferring energy to the battery of the wristwatch compared to charging devices presently commercially available.